Field of the Invention
The present invention relates to an ultraviolet irradiation device, and particularly relates to an ultraviolet irradiation device that irradiates ultraviolet rays from outside a tube in which a fluid flows.
Description of the Related Art
There is known an ultraviolet irradiation device for use in inactivation of bacteria and viruses in a fluid, decomposition of harmful substances in a fluid and the like by irradiating the fluid with ultraviolet rays.
For example, Patent Literature 1 discloses an ultraviolet irradiation device of an external irradiation type. In this device, a tube having an ultraviolet ray transmitting property is spirally wound and is disposed in a casing, ultraviolet lamps are disposed inside the spiral, and the fluid which flows in the tube is irradiated with ultraviolet rays from outside the tube. Patent Literature 1 discloses that when the tube of polytetrafluoroethylene with a high ultraviolet ray transmissivity is spirally disposed, some of the ultraviolet rays irradiated by the ultraviolet lamps are directly absorbed by the fluid to be irradiated in the tube which is spirally wound, whereas a remainder is repeatedly reflected in gaps in the tube and gradually absorbed by the fluid, and that the utilization efficiency of ultraviolet rays can be, therefore, improved. The ultraviolet irradiation device of the externally irradiation type in which the tube is spirally wound like this also can effectively irradiate the fluid having a low transmissivity with ultraviolet rays by making a tube diameter small and stirring the fluid by the spiral.